Pressure regulator



Dec. 3, 1935. A. PFAU PRESSURE REGULATOR Filed July 18, 1954 3 Sheets-Sheet l Dec. 3 A. PRESSURE REGULATOR Filed July 18, 1934 3 SheetsSheet 2 llll Dec. 3, 1935. A. PFAU PRESSURE REGULATOR Filed July 18, 1954 5 Sheets-Sheet 3 Patented Dec. 3, 1935 UNITED STATES PATENT OFFICE PRESSURE REGULATOR Arnold Pfau, Milwauke e, Wis., assignor to Allis- Application July 18, 1934, Serial No. 735,814 11 Claims. (01. 253-24) This invention relates to improvements in control systems for hydraulic turbines and more particularly to means for limiting variations in the pressure of the fluid supplied to a turbine.

Hydraulic turbines are frequently supplied with operating fluid flowing through a pipe line or penstock under a predetermined hydraulic head. The fluid being confined within the penstock, any energy due to reduction or stopping of flow cannot be dissipated and such energy often results in wide variations in penstock pressure which may be dangerous to both the penstock and the turbine. During operation of the turbine, it however becomes necessary to vary the quantity of fluid flowing hence varying the pressure in the penstock dependent on the prevailing condition of operation. Variation in flow must be taken up either in a reservoir capable of receiving excessive flow of fluid upon reduction in quantity of fluid required and of supplying fluid when the quantity of fluid required is increased or means must be provided to permit discharge of the excessive flow during the period when the quantity required for operation of the turbine is suddenly decreased. Such reservoirs or surge tanks are however impractical under some conditions and other means for regulating the penstock pressure, such as a pressure relief valve, must be provided. Such valves should be operable either synchronously with or relatively to the operation of the flow control means of the turbine and should be so constructed as to have entirely selfcontained operating mechanism which merely require a control impulse to commence the operating action. On no account should such relief devices be dependent, for their operating force, on the means for operating the gate of the turbine to secure proper relief action.

It is therefore among the objects of the present invention to provide a control system for hydraulic turbines in which a penstock pressure relief device is provided and is operable in response to a control impulse and without the supply of power thereto from an auxiliary or outside power device.

Another object of the invention is to provide a control system for hydraulic turbines in which a penstock pressure relief device is provided with means to secure positive opening or closing of the discharge opening from the penstock.

Another object of the invention is to provide a control system for hydraulic turbines in which a pens-took pressure relief device is provided with means to prevent or retard movement of the turbine gate upon failure of the relief device to operate.

Another object of the invention is to provide a control system for hydraulic turbines in which a penstock pressure relief device is interconnected with the turbine gate control mechanism to se cure either synchronous operation with or relative operation of the relief device to the turbine gate. I

Another object of the invention is to provide a control system for hydraulic turbines in which a penstock pressure relief device is operable dependent on the rate of movement of the turbine gate.

Objects and advantages other than those above set forthwill be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 is a somewhat schematic view of a hydraulic installation with a diagrammatic showing of the. governor and governor control means by which the operation of the gate of the hydraulic turbine is controlled and with a diagrammatic illustration of the relation of the various elements of the penstock relief device or pressure regulator to the other portions of the structure comprising the installation;

Fig. 2 is a vertical cross sectional View disclosing one embodiment of means for controlling pressure variations within a fluid supply conduit to a hydraulic turbine;

Fig. 3 is an enlarged partial view of the piston and the valve control therefor of the dashpot forming a portion of the structure illustrated in Fig. 2;

Fig. 4 is a modified form of a pressure regulator for use with hydraulic turbines to control pressure variations in the supply conduit to a hydraulic turbine;

Fig. 5 is a partial horizontal sectional view taken on the plane V-V of Fig. 4 to illustrate the pas- 40 sageways for the supply of fluid under'pressure to a portion of the structure of the pressure regulator; and

Fig. 6 is a horizontal partial sectional view taken on the plane VI-VI of Fig. 4 and illustrating the 5 construction and arrangement of the fluid pressure passageways in the regulator at the plane.

Reference numeral I6 generally designates a hydraulic turbine herein illustrated as being of the reaction type and as being supplied with operating fluid from a penstock (not shown) through a spiral casing l1 and discharging into a draft tube l8. Supply of fluid from the spiral casing I1 is controlled by a gate l9 composed of movable vanes I5 connected with a shifting ring thereby decrease the valve generally designated at 4| I4 having an upward extension 2|. The shaft 22 may take place externally thereof to some other of the turbine herein illustrated is provided with point.

a speed governor 20 of which the speed sensitive Due to the connections of the control valve of member comprises the flyballs 23 connected with a collar 24 arranged about the shaft and movable in a vertical direction along the shaft as the flyballs are thrown outwardly by centrifugal force or are drawn inwardly due to the tension of the springs I3 connecting them, upon the reduction of such force. Movement of the collar 24 causes rocking of a bell crank lever 26 mounted on a fixed pivot I2 and movably connected at one end thereof, through a suitable link II, with a lever 21, the other end of which is also movable as will be described hereinafter. A lever 28 is movably connected with the lever 21 and is connected through another bell crank lever 29 with the rod I9 of a piston valve generally designated by 3I. Valve 3! is supplied with fluid from a source (not shown) which is preferably under constant pressure, through a conduit 32 and controls the flow of fluid through conduits 33 and 34 to opposite sides of the piston of a fluid pressure operated servo-motor 36. The piston rod 31 of the servo motor is movably connected through a link 38 vwlth the shifting ring I4 and the lever 21 is movably connected with the piston rod 31.

When the turbine speed increases, flyballs 23 are forced outwardly and the collar 24 is raised. Such action rocks lever 26 which acts through levers 2T, 28 and 29 to shift the piston 0f the valve 3! which changes the connection of the pressure source with the servo-motor 36 and the servo-motor moves shifting ring I4 to change the position of the vanes of the turbine gate I9 to quantity of fluid passing into the turbine, thus reducing the speed thereof. If the speed of the turbine is reduced rather than increased, the operation above described is reversed to increase the flow of fluid through the turbine and thus to increase the turbine speed. Due to the fact that the above speed control is well known and does not form one of the novel features of the invention, the control has been described only insofar as is required to permit complete understanding of the invention associated therewith. As shown in Fig. l of the drawings, the turbine is in normal operation and the turbine gate I9 is completely opened.

When the load on the turbine changes, as when load rejection is'taki'ng place and the gate I9 is being closed due to increase in speed of rotation of the turbine, pressure rises occur in the penstock due to retardation of the rate of movement of the water column in the penstock. Such pressure rises must be minimized or prevented by a pressure regulator which is essentially a relief and is connected between the spiral casing I1 and a discharge conduit 42 which is connected with the tailrace 9. Valve 4! is herein shown as being of the type in which the flow of fluid therethrough is controlled by a valve body which is operated by a device acting under fluid pressure. The, admission of fluid pressure to the valve operating device is regulated by a control valve within the regulator structure which valve is connected with a source of fluid pressure such as the penstock by way of a conduit 44. Discharge from the piston or fluid pressure surfaces of the relief valve is regulated by the control valve I3I and such discharge may take place either into the dis charge conduit 42 of the relief valve as illustrated in one embodiment of the invention or close the turbine gate I9, the pressure regulator is so operated that the pressure relief valve thereof is open and vice versa or the several portions of the structure may operate relative to each other due to the action of the dashpot I as will be apparent hereinafter.

The regulator in general comprises a dashpot subcombination I, a control valve subcombination I3I and a pressure relief valve to control the occurrence of conditions which might cause pressure variations within the penstock. The relief valve itself is generally designated by the reference numeral I2I and is arranged in the bend of the discharge conduit 42 and is in the form of a hollow substantially cylindrical member with a frusto conical end which provides a discharge port I22 for a purpose which will appear hereinafter. The relief valve I2I rests on a seat formed in the conduit 42. The central portion of the valve body is constricted thus providing annular piston surfaces I26 and I21 on which the penstock pressure acts. The upper piston surface I2! is however larger than the lower piston surface I26 so that the valve I2I is normally urged or biased upwardly in a direction to allow discharge of water through the valve and into the tailrace 9. A:

partition I28 provided with a. port I29 is formed across the interior of the valve body I2I and together with other portions of the valve body provides a piston surface I30 which, when pressure is admitted thereto, overcomes the bias of the valve I2I in the opening direction and retains the valve in its closed position as shown.

The port I29 is opened or closed by a valve I3I with a stem 6 extending upwardly and forming a portion of the rod 43 for the piston of a dashpot I to be described. The partition I23 is formed with a hollow cylindrical upward extension I32 which projects through a chamber 50 connected with inlet pressure conduit 44. The stem 6 of valve I3I is guided and sealed in a sealing gland I33 extending downward into extension l32. The valve stem 6 is provided with a collar I34 which limits the movement of valve I3I by abutting against the lower end of gland I33 and provides for a direct connection of the dashpot piston and the relief valve I2I. Fluid entering through conduit 44 may flow through ports I36, port I31 controlled by valve I3I and port I33 into the chamber 5| above piston surface I3I). The fluid is discharged from piston surface I30 through port I29 and through valve I2I upon movement of valve I3l.

The control valve I3I is operated by a dashpot I which includes a cylindrical extension M! from the casing of valve I2I for supporting and guiding a movable cylinder I42. A piston I43 is formed as a portion of the extension of the stem of the control valve I3I and operates within the cylinder I42 upon movement of a yoke 52 connected with the cylinder I42, the yoke 52 being connected with a bell crank lever I46 and links 53 operated by the pushrod 49. The piston I43 is formed with two bypasses to allow flow of fluid from one side of the piston to the other 2,022,975 3 tures into the passageway on each side of the ton I43 rapidly. Such upward action of the piston. Flow of fluid through the passageway piston is, however, limited by the restriction of I5I is controlled by a needle valve I52 which exthe bypass I 5I by the needle valve I52 and by tends through the piston rod and is adjustable the action of the slide valve I51 which latter at the upper end thereof in anysuitable manner. closes after a predetermined pressure difference 5 The other bypass is formed by passages I53 and is produced between the two sides of the piston. I54 formed in the piston I 43 and connected by'a During the first few moments of the movement passageway I56 through a floating slide valve of the cylinder I42 the pressure produced below. I51 reciprocable in a chamber formed in the the piston acts on the slide valve member I51 to piston. The position of the slide valve I 51 is compress the spring I 58, thus closing the ports controlled by the degree of compression of a I53 and I54. Fluid can then flow from the lower spring I58 abutting against one end of the valve side of the piston to the upper side thereof at a and the degree of compression of a spring I59 rate determined only by the setting of the abutting against the other end of the valve. The needle valve I52. The piston I43 therefore lifts. spring I59 together with a pin I6I forms a mov- Such lifting of the piston I43 lifts the control able coupling which, in some positions of the valve I3I from its lower seat thereby releasing piston I43, abuts against an adjustable stop I62 discharge fluid pressure through the port I29 mounted on the cylinder guide I M and extendpreviously closed by control valve I 3I and ing into the cylinder I42 through asuitable sealshutting off supply of fluid through the port ing gland. I38. During movement of the control valve The operation of the regulator will now be from one of its seats to the other, fluid pressure described, considering the various operations from the conduit 44 discharges through ports thereof enumerated below, from the position I29 and I22 thus relieving pressure on the piston shown which is the position when operating fluid surface I30. The relief valve I2I then opens due under pressure is being passed through the turto the higher pressure on the piston surface I21. 25 bine; considering separately the condition (at) Opening of the valve I2I tends to again seat the when the turbine gate is slowly closed, the concontrol valve I3I to close port I29 but upward dition (b) when the turbine gate is rapidly movement of the piston I43 has continued until closed, the condition (0) when the turbine gate the turbine gate I9 is fully closed when both the is being opened with the pressure relief valve in dashpot cylinder I 42 and the piston I 43 are in 30 closed position as when the turbine is being their extreme upper position. If the turbine started, the condition (d) when the turbine gate gate I9 then remains closed, the force acting to is again opening with the relief valve still parcause piston I43 to remain disappears because tially open and when load change takes place, the pressures on both sides of the piston are and the emergency condition (e) when the relief equalized by fluid flow through the bypass I 5I valve 15 off its seat and is sticking when the and bypass I51 reopens due to action of spring turbine gate is being either opened or closed. I58 which now expands. Due to the connection In condition (a) when the turbine gate is of valve I3I with piston I43, the valve gradually slowly closed, the pushrod 49 slowly moves todrops, thus closing port I29 and causing pressure ward the left and tends to lift the dashpot 'cylto build up on piston surface I30 whichrecloses inder I42 thereby tending to lift piston I43. valve I2I. Fluid within the cylinder is compressed below In the condition (0) when the turbine gate is the piston I43 and flows through the bypass I5I slowly opening with the relief valve in closed poand through the bypass formed by the passagesition, it being desired that the relief valve reways I53, I54 and I56. The excess of the presmain closed, the pushrod 49 moves toward the sure below the piston I43 over the pressure above right, thereby depressing cylinder I42 which prothe piston acts on the slide valve I51 and tends duces an overpressure above piston I 43. Floating to compress the upper spring I58. Piston I43 is valve I51 may be closed and fluid therefore may connected with the control valve I3I and reflow between the sides of the piston at a rate demains in the position shown as long as the extermined by the free area of only the bypass ISI. 50 cess pressure below the piston is not suflicient to Valve I3I therefore remains closed, retaining cause valve I51 to close. The piston I 43 therepressure on piston surface I30 which keeps valve fore remains in the position shown and control I 2| closed. Unretarded slow movement of the valve I3I remains in its lowermost position, thus gate I9 is thus permitted and the pressure reguretaining the fluid pressure on relief valve piston lator relief valve remains closed. 55 surface I 39 and keeping the valve closed. As In condition (d) when the turbine gate is again long as the pressure on the piston I43 does not opening and when the relief valve is still partially exceed a predetermined amount, the slide valve open, if the turbine load decreases, slow closing of I51 Will remain p and d may flow through the relief valve, as described under condition (b), the bypass I53, I56 and I54 as well as the bypass is interrupted. When the load again increases 60 e turbine gate may continue to close the turbine gate tends to open quickly and the l wly Without causing any further action in the rod 40 tends to move quickly toward the right. pressure regulator other than continued upward The cylinder I42 is then depressed, thus depressmovement of the cylinder I42. The cylinder is ing piston I43, and causing piston I43 to move so dimensioned that Such upward movement substantially with movement of the cylinder I42. may c nt n e until the turb n t is fu ly Valve I3! is then depressed until port I3! is closed. The cylinder I4 then em in the opened and port I29is closed. Pressureis applied lift p si i n ntil th ur ine ga i gain to piston surface I30 and valve |2| then closes. opened when a reverse movement takes place If the relief valve should stick when off its seat which will be described hereinafter. in condition (e), an emergency arises which the In the condition (1)) when the turbine gate is valve and the pressure regulator as a whole must rapidly closed, the various element-s of the regumeet. Such sticking may occur either when the lator being in the position shown, rapid moveturbine gate is closing and the valve is opening ment of the pushrod 49 takes place toward the or when the turbine gate is opening and the valve left and lifts the dashpot cylinder I42 and pisis closing. When the gate is closing, pushrod 49 is moving toward the left, lifting cylinder I42 and producing pressure under the piston I43 which lifts the valve I3I. Supply of pressure to the piston surface I30 is therefore interrupted and 1 the fluid under pressure on the piston surface is allowed to discharge. The relief valve I2I will therefore open. If the valve I2I sticks, upward movement of the piston I53 continues only until the collar I34 is firmly seated against the end of the sealing gland I33. Continued upward movement of the cylinder I42 produces suflicient pressure below the piston to close the slide valve I51, the valve I51 moving away from stop I62. The piston I43 being now positively locked with valve I2I, the servo-motor 36 must move the valve or be retarded to a ratedependent upon the resistance of the sticking valve I2I. If the valve cannot be moved at all, the servo-motor can close the gates only at a rate dependent upon the rate of fluid flow through the piston bypass I5 I. The closing gate motion is thus retarded to such slow rate as will not cause dangerous pressure increases in the penstock or the spiral casing attached thereto.

When the gate I9 is opened and the valve I2I is closing and sticks during the closing operation,

' the reverse of the above action takes place with the piston surface Hi the exception that the control valve I3I closes the discharge port I29 and opens the supply port fist, thus applying pressure on the piston surface I38 which tends to close the valve.

In the modification of the present invention illustrated in enlarged detail in Figs. 4, 5 and 6, the pressure regulator is disclosed as again comprising a pressure operated relief valve 4I a valve IZiI for controlling the supply of fluid pressure to, and the discharge of pressure from, the several piston surfaces of the relief valve, and a dashpot 1 connecting the control valve I3I with the lever system leading to the shifting ring I4 as shown in Fig. l. The dashpot is similar, in its construction and operation, to that illustrated and described relative to Figs. 2 and 3 and, therefore, re-

quires no further description.

The relief valve I2I of the embodiment disclosed in the figures now under consideration, is again a hollow substantially cylindrical member with a constricted central portion forming piston surfaces 52?; 4 conical surfaces forming a piston surface Ill and is formed with a member I12 extending upward and closing off the interior of the valve from the end thereof. The member I12 is substantially cylindrical and is formed with a plurality of ports and passageways through which the supply of fluid pressure to, and the discharge of fluid pressure from, the piston surface I'II is controlled by the valve I3! which seats in the member I12 and is operated by the dashpot piston I43. When the valve ISI is in theposition shown, fluid pressure from the supply conduit 44 flows in the path indicated by the full line arrows through the passageway I16, the port I11, the passageway its and the port I19 into the chamber above the piston surface III. Such surface area plus the area of the piston surface I26 is greater than the area of the piston surface I21 and the valve is accordingly held in its closed position. When the control valve I3I is raised to close off the port I11 and to open the port I13, flow of fluid through the passageway I16 and the port I11 is blocked and fluid may discharge from above by a passageway indicated by dotted line arrows through the port I19, port W3, the port I8I and the passageway I82 into and I21, and is formed with frusto-' the discharge chamber I83 connected with the discharge conduit 46. It will be seen that the valve I3I may move relative to the member I12 by the distance between the collar I34 and the end of the sealing gland I33 by which the stem 5 of valve I3I is sealed in the extension I12. The extension I12 is secured to and moves with the relief valve I2I, thus requiring that suitable sealing glands be provided between the pressure supply passageway I16 and the discharge chamher I83 and also between the discharge chamber I83 and the interior of the dashpot cylinder guide MI.

The operation of the embodiment of the invention described immediately above'will now be 5 considered relative to the same conditions as were previously considered in explaining the operation of the embodiments first illustrated and described in the present application. It'is again assumed that the turbine gate is open and that 20 the pressure regulator is closed, all portions of the regulator being then in the position shown in the drawings.

When the several elements of the pressure regulator are in the positionshown in the drawings and the turbine gate is being slowly closed, the operation of the modification now being considered is the same as was previously described. The gate is may continue to close slowly without producing any material pressure increases in the penstock.

When the turbine gate is closing quickly, the

a relief valve I2I being in closed position as shown,

the pushrcd 49 moves quickly toward the left, thus producing a high pressure in low the piston I43. The floating slide valve I51 closes and the pressure in the lower portion of the cylinder I42 forces the piston I43 to rise which lifts the valve I3! to close port I11 and to open 'port I13. The supply of'fiuid pressure to the piston surface I'II is thus cut off and the fluid pressure discharges from above the piston surface through the ports I19, I13, IIlI, the passageways I82 and I83 as indicated by dotted line arrows. The penstcck pressure on the piston 45 surface I21 then lifts the valve Ill and allows discharge of water from the spiral casing through the tube 42 to the tailrace 9 which limits pressure rises in the penstock and the spiral casing I1. When movement, of the rod 49 and hence 50 lifting of the cylinder I42 has reached its end position, thegate I9 is fully closed. Piston I43 is then in its uppermost positionand is stationary due to equalization of pressure on the two sides of the piston. The force acting'on the valve I 3I causes piston I43 to drop slowly, thus opening the supply port I11 and closing off the discharge port H3. Pressure is then again applied to the piston surface I1! through the supply conduit 44, the passageway I15, port I11, passageway I18 and 0 the port I19 as indicated by the full line arrows. Valve I2I then slowly closes at the rate of oil flow through both bypasses in the dashpot piston Hi3, and flow of water through the penstock is completely out off. a 5 When the gate I9 is opening slowly while the relief valve I'ZI is still closed as in starting operation of the turbine, the pushrod 49 moves toward the right and the cylinder I42 is slowly depressed. Valve I51,being in contact with stop I62, cannot however close and fluid may thus flow through both bypasses between the two sides of the piston M3 thus preventing production of substantial pressure above the piston. The piston, therefore, remains stationary or is very slight- 15 the fluid be- 35 and when the load increases. causes movement of the rod which lifts cylinder I42 below the piston I43.

Closing of the gate 49 toward the left, and produces pressure accordingly remains stationary or tends to be only slightly lifted and the control valve I3! is kept down which keeps port H3 closed. Pressure is retained on the piston surface Ill and the relief valve I2l continues to close. If a sudden load decrease now occurs, the movement of rod 49 and of cylinder M2 is accelerated which produces such pressure below piston M3 to open valve I31 and allows relief valve I2| of reopen, thus decreasing the quantity of water flowing through the turbine to decrease power produced thereby as required by the system. If a sudden load increase, however, takes place, the rod 49 accelerates its movement toward the right, thus depressing cylinder I42 which depresses control valve i3! to close the discharge port I13. Fluid pressure is then supplied to the piston surface Ill and valve I25 is closed to prevent further discharge of water now required for operation of the turbine. The gate l9 may then continue to open until equilibrium flow conditions are established without further movement of the regulator.

Under the condition previously mentioned,

I when the gate is being opened and the pressure regulating valve is being closed, the rod 49 is moved toward the right and the cylinder I42 is depressed to retain the control valve l3| in the lowermost position, thus keeping port I13 closed which retains the pressure on the piston surface ill and causes the relief valve l2! to continue to close. If the valve should now stick, emergency condition e arises, during the closing operation thereof, the downward movement of the piston i413 continuing, a force from the servo-motor 36 is applied to the valve I 3| and hence to the valve I21 to tend to close the latter. Resistance of the valve to movement retards the movement of the servo-motor and the gates can open only at the rate of movement of the dashpot piston I43 in the cylinder I42. When the gates are closing and the regulator is opening, if sticking of the valve 12! should occur, the reverse actions to those above described takes place, thus limiting pressure increases in the penstock.

Although but two embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and Patent:

1. A control system for hydraulic turbines comprising means controlling the flow of fluid through he turbine, means controlling the operation of the first said means, a dashpot connected desired to secure by Letters with the first said means and operated thereby, a fluid pressure operated valve connected with pressure applied surfaces.

2. A control system for hydraulic turbines comprising means controlling the flow of fluid through the turbine, means controlling the oper- 15 of flow of fluid pressure supply to said relief valve to control the flow of fluid pressure to and from said relief valve.

4. A regulator for limiting pressure variations 40 in the fluid owing through a hydraulic turbine sageways to the piston surfaces of valve.

5. A regulator for limiting pressure variations in the fluid flowing through a hydraulic turbine of fluid pressure to said relief 5 valve.

6. A regulator for limiting pressure variations in the fluid flowing through a hydraulic turbine tive movement of the cylinder and the piston and a bypass unaffected by such relative movement,

- and a valve directly connected with said dashpot to control the flow of fluid pressure to said relief valve.

'7. A regulator for limiting pressure variations through a hydraulic turbine and comprising a fluid pressure operated valve connected with the turbine to relieve excesses in pressure of the fluid supplied thereto, a dashpot actuated in response to the quantity of fluid flowing through the turbine, said dashpot including a movable cylinder with a piston movable therein, and a valve rigidly connected with the piston of said dashpot to control the flow of fluid pressure both to and from said relief valve.

8. A regulator for limiting pressure variations in the fluid flowing through a hydraulic turbine and comprising a fluid pressure operated valve connected with the turbine to relieve excesses in pressure of the fluid supplied thereto, said valve having differential piston surfaces and being formed with passageways therein, a dashpot actuated in response to the quantity of fluid flowing through the turbine, said dashpot including a movable cylinder with a piston movable therein, and a valve rigidly connected with the piston of said dashpot to control the flow of fluid pressure through the passageways to and from the piston surfaces of said relief valve.

9. A regulator for limiting pressure variations in the fluid flowing through a hydraulic turbine and comprising a fluid pressure operated valve connected with the turbine to relieve excesses in pressure of the fluid supplied thereto, said'valve having differential piston surfaces and being formed with passageways therein, a dashpot actuated in response to the quantity of fluid flowing through the turbine, said dashpot including a movable cylinder with a piston movable therein having a bypass, and a valve rigidly connected with the piston of said dashpot to control the flow of fluid pressure through the passageways to and from the piston surfaces of said relief valve, and means for retaining the bypass in a predetermined position during closed position of said relief valve.

10. A regulator for limiting pressure variations in the fluid flowing through a pipe line and comprising a fluid pressure operated valve connected with the pipe line to relieve excesses in pressure of the fluid flowing therethrough, a dashpot actuated in response to conditions causing pressure variations in the pipe line and including a movable cylinder having a piston movable therein, the piston having a plurality of bypasses independently operable under different pressure conditions in the cylinder, and a valve connected with said dashpot to control the flow oi fluid pressure to and from the actuating means of said relief valve.

11. A regulator for limiting pressure variations in the fluid flowing through the servo-motor operated gate of a hydraulic turbine and comprising a fluid pressure with the turbine to relieve excesses in pressures of the fluid supplied thereto, a dashpot actuated in response to conditions causing pressure variations in the fluid flowing through the turbine and including a movable cylinder having a piston movable therein, a valve rigidly connected with the dashpot piston to control the flow of fluid pressure both to and from the actuating means for said relief valve, and means for limiting the operated valve connected 5 stroke of said control valve and for indirectly but positively connecting said relief valve with the servo-motor for partially controlling operation thereof under predetermined conditions of operation of the regulator.- I

ARNOLD PFAU. 

